1. Field of the Invention
The invention relates to a heat treatment device in the development of photographic paper.
2. The Prior Art
The processes for the development of photographic material often include heat treatment stations. The recording material there is guided along heating surfaces, smoothing devices, etc. The recording material is usually a paper carrier with a specially prepared coating for picture recording. Typically, the paper to be developed contains an exposed dry silver material coating.
Presently known devices for the heat treatment of photographic paper utilize a drum which is covered with fibrous material, such as a textile, felt, or synthetics, or an electrostatically charged nap. The fibrous surface of the drum runs along a heated trough which is curved to be coextensive with the outer radius of the drum and extend along part of the circumference of the drum. In the development process, the photographic paper passes between the drum and the heating trough or surface with the dry silver coated side facing the trough, which is usually metal. The drum serves to pass the paper along the trough because the coefficient of friction of the paper against the drum is higher than the coefficient of coating against the trough. It has been discovered, however, that this arrangement for the transport of paper along the trough often breaks down and that the coefficients of friction become identical or even reversed. A manner by which this occurs is due to the slight tendency of the relatively cold coated side to stick against the heated trough surface; while the drum surface fibers contacting the other side of the paper become slowly displaced toward the direction opposite the rotation of the drum during the periods when the drum runs against the surface of the trough between developments. Inclination of the exterior fibrous surfaces of the drum away from the direction of rotation produces the coefficient of friction between the paper and the drum. This deterioration of the relative frictional settings desired for the drum and trough device alters the heat treatment process carried on by the trough, making the developing system less reliable.